We have installed catless AR 3" DP. At Stage 2 GIAC software flash, it is worth about 8-12 whp over OEM. Catted version will be a bit less. The OEM DP's are actually very efficient and aren't the same ones BMW installed on the 135i and 335i.

Thx, i'm considering downpipes to increase the sound but a bit extra power is always welcome

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I replaced a mid pipe last week on a IM so i did a comparison of dumps looking from the dump outlet as we have many stock cats in stock .
I could not see any difference, the cat component looks the same as a stock 135/335 cat, i reckon the extra power comes from a better tune i guess time will tell.

Can anyone running catless DP's comment on the smell? I know the turbo motors run cleaner than NA but I just dont know if I'd be able to live with it.

I have been told by several buddies with N54 motors that running no cats smells BAD especially in traffic. I was going to go with cat free DP but after talking to them I am leaving them and just doing post cat 1 section back.

Can anyone running catless DP's comment on the smell? I know the turbo motors run cleaner than NA but I just dont know if I'd be able to live with it.

Although the direct injection engines run more efficiently you will still get the unburned hydro carbon smell, especially if you were just sitting in traffic. If you were to keep the oem mid pipes in place, the smell is cut down a bit.